Good question. For one thing, WordNet 2 was release too late in our development cycle for us to even consider putting it into Thesaurus 1.0 unless we wanted to delay release for some time. Right now, WordNet 2 does not offer enough new things to warrant all that effort. But, we are continuously reviewing this sort of thing, so you might see it in a future release.

From Princeton's site: "WordNet 2.0 includes more than 42,000 new links between nouns and verbs that are morphologically related, a topical organization for many areas that classifies synsets by category, region, or usage, gloss and synset fixes, and new terminology, mostly in the terrorism domain." Aside from the last bit, these do not sound like minor changes. But of course, beggars cannot be choosers and what you have provided is most welcome. Thanks.